Sulfite liquor treating processes and products



' Patented Feb. 19, 1952 SULFITE LIQUOR TREATING PROCESSES AND PRODUCTS Curt Uschmann, Lebanon,

Oregu, assignor to Cascades Plywood Corporation, Portland, reg., a corporation of Delaware Application October 13, 1947, Serial No. 779,485 Claims. (Cl. 26017.2)

My invention relates to the preparation of a binder from the waste liquor of the suliite pulp manufacturing process. Such waste liquor presents a problem of disposal to prevent contamination of bodies of natural water into which it is customarily dumped, yet it contains wood components, including cellulosic and lignin materials, carbohydrates, ketones, terpenes and natural resins, which, by my process, may be converted into a valuable by-product of the pulpmaking process.

The principal object of my invention, therefore, is two-fold: first, to render sulfite waste liquor innocuous, and, second, to recover from it a by-product which is useful in itself as a varnish base, as a moldable plastic, and as a thermal-setting binder for various purposes, or which can be combined with other ingredients to form such products, or can be used as a hardening medium for synthetic rubber products. Such binders are of particular value in fabricatin wood products, such as for manufacturing wallboard, synthetic lumber, and a variety of pressed or molded articles using woody material fibers procured from wood waste, bagasse, corn stalks, etc., or for bonding veneer sheets in the manufacture of plywood and in veneering furniture.

It is a particular object of my process to employ a treatment procedure which, while being effective to convert the useful ingredients of the sulfite waste liquor into binder material, can be carried out economically by utilizing simple equipment, by adding to the liquor in the recovery process only small amounts of inexpensive materials, and by accomplishing the refining treatment in a short period of time.

Depending upon the particular purpose for which the resultant binder is to be used, the process may be varied to alter the proportions or types of ingredients added to the sulflte liquor during the recovery process, or blended with the resultant product of such process after its completion.

Details of my preferred process are described more particularly hereafter, and in the drawings representative apparatus suitable for use in the performance of such process is illustrated.

The figure of the drawings is a top perspective view of apparatus which may be usedin conjunction with my process, elements of it being shown rather diagrammatically and parts being broken away to disclose features of its construction.

The process of reclaiming binder-forming materials from waste sulfite liquor and treating it to produce binder consists generally of heating the suliite liquor, preferably to the boiling point, and at intervals during such heating process adding reactive ingredients to it. The first step during such heating process, following its concentration to greater or lesser extent, if desired, is to alkalize the liquor with a caustic alkali, such as sodium or potassium hydroxide.

After the alkalized liquor has been heated for a length of time sufllcient to render it uniform, the aldehyde furfural is added to the liquor. Again the heating is continued for a ti e suflicient to insure the substantial completion of the reaction between components of the liquor and the added aldehyde. For certain purposes the product obtained from the treatment of the waste sulflte liquor to this point may be util zed as a binder, such, for example, as in themanufacture of low density fibrous products from woody fibers impregnated with such binder.

Alternatively the process may be continued, and while the liquor is still hot, phenol can be added to it. The resulting product ha excellent water-proof and binding qualities, suitable either for use in making fiber products, s ch as hard board or synthetic lumber by admixture with fibrous woody material, or as an adhesive for veneer in the manufacture of plywood or furniture.

It is possible to treat waste sulflte liquor in the manner described generally above in a batch process, but this is comparatively slow, because after treatment of one batch has been completed, the heating of the new batch must be started and the various steps described must be performed sequentially before afurther batch can be treated. Preferably the process steps are carried out simultaneously on various portions of li uor passing step-by-step through apparatus, such as from one container to the next, one ste of the process being performed in each container.

The apparatus shown in the drawing includes a storage reservoir l for waste sulfite liquor from which it may be drained through a pi e I0 continuously at a rate which may be determined by adjustment of the valve H in that pipe. The liquid in flowing out of the pipe preferably is discharged from a header l'2 perforated along its lower side, which extends along one edge of a heated concentrating device or vaporizer 2.

The concentrating device includes a shallow pan 20 inclined from its edge beneath header pipe I! gently downwardly to its discharge opening 2 l. Preferably the discharge opening extends entirely across the lower edge of the pan, or nearly so, and the size of its opening may be regulated by suitable means (not shown) if desired. The

bottom sheet of the pan is heated by hot fluid. steam for example, circulated through a lower chamber 12 of the vaporizer 2 beneath the pan 20. The hot fluid may be supplied to such chamber through a pipe 23 and exhausted through a pipe 24, so that the hotter fluid will pass beneath that portion of the pan adjacent to the discharge opening 2|, although the direction of circulation is optional. The fluid may be released into the heating chamber, or circulated through it confined in heating coils, as may be preferred.

Because the header l2 distributes the sulflte liquor over substantially the entire width of the vaporizer pan 2., it will flow downwardly to the' discharge opening 2| at a velocity determined by the angle at which the pan is tilted. Preferably passage over the pan will require not less than minutes, and should be at least sufllcient to raise the temperature oi the liquor to its boiling'point. During this passage preferably a substantial portion or the water will be evaporated from the sulflte liquor, the amount depending upon the temperature of the sheet, the velocity of the liquid over it. and the quantity of flow regulated by the adjustment of valve although such concentration of the liquor is not essential. The resulting steam and fumes, such as sulfur dioxide and of terpenes vaporized, will be collected by the hood 2! covering the pan 20, and will be conducted by pipes 23 out of the pan to remove objectionable vapor.

The more or less concentrated liquor flowing out of the pan 2!! through the discharge opening 2| is deposited in one end of a tank 3 which has a plurality of parallel partitions 30, alternate partitions projecting from opposite sides of the tank across the major portion of its width to forma serpentine trough for flow of the liquor from its inflow end adjacent to vaporizer 2 to a discharge opening 3| at its opposite end. During the passage of the liquor through this trough, its heating is continued by circulating hot fluid, such as steam, through a compartment 32 beneath the tank 3. Such fluid may be supplied to this chamber through a pipe 34 and discharged from it through a pipe 35. Again such fluid may be released directly into the chamber, or circulated through heating coils. Preferably this tank is substantially horizontal so that the liquor will fill the serpentine trough to a considerable depth controlled by the height of the weir at the entrance to the outlet 3|.

To the liquor in tank 3 caustic alkali is added in controlled amount, preferably being supplied near the inflow end of its serpentine trough. The caustic may be stored in a container 33 from which it is fed through pipe 31- into the tank in an amount controlled by regulation of valve 33. From such tank the hot alkalized liquor is poured into a vat 4 throughthe discharge spout 3|.

This vat is heated by hot fluid, such as steam, supplied through a pipe 40 to the space 4| between inner and outer walls of the vat, from which jacket space the fluid is discharged through pipe 42. While in this vat, the liquor not only is heated, but is stirred continuously by the paddles 43 of an agitator, which are carried by a rotary shaft 44.

To the liquor heated in vat 4 is added the aide-- hyde. Conveniently this can be stored in a supply tank 41 and dispensed at will through pipe 43, in quantities controlled by valve 43 in such pipe, into the trough 3| to mix with the liquor as it flows into the vat. The contents preferably are heated to boiling temperature, substantially in a thin sheet 4 that of water, and the agitation is continued until the interaction of the aldehyde and liquor components is complete, the time required being between five and thirty minutes. Ebullition oc-- curs during the reaction betweenjthe alkalized sulflte liquor and furfural in the absence of phenolic' bodies. Completion of this reactionis indicated by change in color of the liquor from practically colorless to a light brownish tint.

Since vat 4 is part of continuous treatment apparatus, liquid is withdrawn continuously through the outlet pipe 45 controlled by opening valve 43. Its separation from the rest of the liquid is effected by gravity. The upper paddles of agitator 43 propel liquid upward. whereas lower paddles on it (not shown) propel liquid downward, forming two zones of circulation. As

' the cooking progresses the heavier reaction products settle to the lower zone from which they are drained through the outlet. The time of treatment is established by the rate of inflow through spout 3|, th valve 48, after the vat is full, being regulatedto maintain the height 'of the liquid in the vat constant.

The liquid removed from vat 4 may be used in that form as a binder for low specific gravity, woody fiber products, such as wallboard of insulating type which is not intended to withstand appreciable mechanical stresses. Preferably, however, the liquid is processed further by discharging it from the outlet 45 of such vat into a second vat 5 similar in character to the vat 4. This vat also is steam jacketed, or jacketed for heating by other hot fluid, supplied to the jacket space through pipe 50 and discharged from such space through pipe 5|. This vat likewise is provided with an agitator, including paddles 32 carried by rotary shaft 33.

The liquid again is heated and maintained substantially at its boiling temperature, which will still be approximately the same as that of water, and during such heating phenol is added to the liquid and stirred into it by the agitator. Such phenol must be heated to keep it fluid if it is to be added in liquid state. A heated or steamjacketed tank 58 may serve as a reservoir for it, and the phenol supplied from it through pipe 51 may be deposited in a trough 58 through which liquid from the discharge spout 45 of vat 4 flows into vat 6, to mix with such liquid. The amount of phenol added is controlled by valve 59.

The reaction between the phenol and ingredients of the liquid again requires flve to thirty minutes for completion, and the agitator 53 is constructed so that its upper blades force liquid upward and its lower blades force liquid downward to segregate the heavier phenol reaction products from the partially reacted portion of the vat liquid. Finally the resulting liquid, having a purple or reddish color characteristic of phenol, is drained from the vat through outlet 34, controlled by valve 55 to maintain the liquid in the vat at a constant level. It constitutes a resinous binder or filler having excellent binding qualities when set by the application of heat and which is highly water resistant. It may be used to bind woody fibers in the manufacture of high density fiberboard, called synthetic lumber or hardboard, or other fiber products having a specific gravity of .9 or higher.

For making woody fiberboard or molded products the amount of binder resulting from the treatment in vat 4 or vat 5 may be mixed with woody fibrous material in proportions of ten to twenty percent or the weight of fibrous material r 8 containing its natural moisture. Such liquid may also be used in making heat setting moldable plastics without woody fiber, and in the manufacture of varnish or plastic paint and of synthetic rubber products to advantage, and such uses of the product are to be recognized, although reference generally is made to it as a binder. The product is very stable and its thermalsetting and strength properties do not deteriorate when stored in open containers, even for several months.

For use particularly in moldabie plastics, the liquid resulting from the treatment in vat I may be concentrated further by centrifuging, precipitation or both. By separation in a large centrifuge a very viscous concentrate, like a paste, is obtained. Alternatively the binder may be concentrated :by precipitation. If an acid is added to the liquid, for example hydrochloric acid, in an amount of one to three percent by weight, a precipitate having excellent thermal-setting properties, when used as a molding substance, after washing and drying, will be produced. Not only is this synthetic resin concentrate waterproof but it is also germ proof and fungus proof and is not readily combustible. The addition to the liquid of not more than one percent by weight of ammonium chloride alone, or accompanied by not more than one-half percent by weight of resorcinol will enable as much as 80 percent by weight of the treated liquor to be concentrated by centrifuging into a viscous concentrate or paste.

While the quantities of material added to the waste sulflt liquor during the recovery process n described may be varied considerably, the caustic alkali used should be between five percent and fifteen percent of the concentrated sulfite liquor by weight, the aldehyde up to about fifteen percent by weight of the concentrated and alkalized liquor going into vat 4, and the phenol up to about ten percent by weight of the treated liquid flowing into vat I. In other words, substantially equal amounts by weight of aldehyde and phenol are preferred.

A specific example of a treatment process which has proved to be quite satisfactory employs the following quantities and times: 100 pounds of raw waste sulfite liquor are heated and boiled at atmospheric pressure for about minutes, during which boiling 5 pounds of sodium hydroxide are added after which the boiling is continued for at least about 5 minutes; 5 pounds'of furfural is added to the alkalized and concentrated liquor and the boiling is continued for a still additional 5 minutes while the liquid is agitated. If enhanced binding and water repellant qualities are desired, the boiling is continued for another 5 minutes after 5 pounds of commercial phenol has been added.

Utilizing the end product of the example given immediately above in the manufacture of wallboard or other fibrous synthetic lumber product, 16 pounds or the resulting binder may be mixed with 100 pounds of woody fibrous material containing its natural moisture, and from this material a fiber sheet is formed and pressed under heat and pressure according to known methods.

As representative of a typical use of the binder material obtained from vat 4, the following example is presented. 1200 parts of wood fiber containing its natural moisture has mixed with it parts of alum dissolved in 200 parts of water, all by weight. With this fiber mass is mixed a solution of 200 parts of the liquid binder diluted ill . pounds per square inch for a with 400 parts of water. The fibrous material thoroughly impregnated by suitable mixing technique with the binder is formed into a mat and then pressed under a pressure. of 175 pounds per square inch at a temperature ranging from 285 to 340 degrees F. The length of time such heat and pressure is applied depends upon the thick ness of the mat and of the resulting board. For a mat to produce a board 5; inch thick, ten minutes will sutlice, whereas if the mat is sufllciently thick to produce a quarter inch board the time required will be 20 minutes.

In anotherwise similar wallbcard manufacturing process the strength and water resistant qualities of the board may beincreased substantially if binder drained from vat 5 is utilized in the same proportions stated above instead of the intermediate product obtained from vat 4. The tensile strength of the board resulting from the use of these processes may be increased if 50 parts of sodium silicate by weight are added to the binder obtained from vat 4 or from vat 5.

As an alternative to the sodium silicate modification, a stronger and more water resistant board than obtained by use of the binders from vats 4 and 5 unmodified may be produced by substituting for the intermediate product from vat 4 or the final product from vat Ii the same quantity of precipitate resulting from acidulation of the binder or of concentrate from centrifuging.

A further example of a fiberboard making process by which a board smooth on both sides may be produced is cited: parts of dry wood fiber material are mixed with 33 parts of the binder liquid obtained from vat 5 by weight. A mat of this mixture can be pressed for 2 minutes at a pressure of 100 pounds per square inch and a temperature of about 340 degrees F.. and thereafter the pressure can be increased to 250 period of approximately 16 minutes. The temperature of the platens may remain substantially constant throughout the pressing operation. During the period of'pressing under lower pressure steam may escape from the board with relative ease,

and after the moisture content has been reduced sumciently, the pressure may be increased, as

stated above, until the pressing operation is completed. I

I claim as my invention:

1. The method of treating waste sulfite liquor which comprises heating the liquor to its boiling point and thereby evaporating a substantial portion of the water therefrom, adding to the liquor caustic alkali, adding furfural to the alkalized liquor, and heating the liquid in the absence of phenolic bodies to its boiling point for at least five minutes.

2. The method of treating waste sulfite liquor which comprises flowing the liquor in a'thin sheet over a surface at a temperature at least as hot as the boiling point of the liquor and thereby evaporating a substantial portion of the water therefrom, draining the liquor thus concentrated into a container, adding furfural to the concentrated liquor, and heating the liquid for at least five minutes.

3. The method of treating waste sulfite liquor which comprises flowing the liquor in a thin sheet over a surface at a temperature at least as hot as the boiling point of the liquor and thereby evaporating a substantial portion of the water therefrom, draining the liquor thus concentrated into a container, adding to the concentrated liquor caustic alkali, adding furfural to the alkalized liquor, and heating the liquid to its boilingpoint for at least five minutes and agitating it while thus heating it.

4. The method of treating waste sulfite liquor which comprises heating the liquor to its boiling point and evaporating a substantial portion of the water therefrom, alkalizing the liquor while heated with to percent of the sulfite liquor by weight of caustic alkali, adding to the alkalized liquor furfural in an amount not greater than 15 percent by weight of the alkalized liquor, and maintaining the resulting liquid at substantially its boiling point for a period of 5 to minutes.

5. The method of treating waste sulfite liquor which comprises heating the liquor to its boiling point and evaporating a substantial portion of the water therefrom, alkalizing the liquor while heated with 5 to 15 percent of the sulfite liquor by weight of caustic alkali, addin to the alkalized liquor furfural in an amount not greater than 15 percent by weight of the alkalized liquor, maintaining the resulting liquid at substantially its boilingpoint in the absence of phenolic bodies for a period of 5 to 30 minutes. thereafter adding to the alkalized liquor and aldehyde liquid phenol in an amount not greater than 10 percent by weight of the liquid to which it is added, and maintaining the liquid at substantially its boiling point for a period of 5 to 30 minutes.

' 6. The method of treating waste sulfite liquor which comprises adding to the liquor caustic 'alkali, adding to the alkalized liquor furfural and phenol, heating the liquid and thereby effecting-a reaction among the furfural, the phenol and components of the liquor, and acidulating the liquid to precipitate from the liquid compounds of the liquor with the phenol and aldehyde.

'7. The method of treating waste sulflte liquor, which comprises adding to the liquor caustic alkali, adding furfural to the alkalized liquor, heating the liquid for at least five minutes, and centrifuging the liquid and thereby segregating from the liquid reaction products of the furfural with the liquor in a thick viscous form.

8. The method of treating waste sulfite liquor, which comprises adding to the liquor caustic alkali, adding-to the alkalized liquor an aldehyde and phenol, heating the liquor and thereby effecting a chemical reaction among the phenol, aldehyde and components of the liquor, and adding to the liquor ammonium chloride in an amount not more than 1 percent by weight of the liquid and resorcinol in an amount not more than percent by weight of the liquid to precipitate from the liquid reactiom products of liquor components with the phenol and aldehyde.

9. The method of treating waste sulfitediquor which comprises adding to the liquor caustic alkali, adding to the alkalized liquor furfural v and phenol, and heating the liquid and thereby effecting a reaction among the furfural, the phenol and components of the liquor.

10. The method of treating waste sulfite liquor which comprises, adding to the liquor caustic alkali, adding to the alkalized liquor furfural and phenol, heating the liquid and thereby eifecting a reaction among the furfural, the phenol and components of the liquor, and adding to the liquor ammonium chloride in an amount not more than one percent by weight of the liquid.

11. A thermal-setting resin binder incorporating the reaction product of furfural with alkalized, concentrated sulfite liquor.

12. The binder defined in claim 11, in which phenol is incorporated in the reaction product.

13. A thermal-setting resin binder includin in aqueous liquid solution at ambient air temperature, the reaction product of furfural with alkalized, concentrated sulfite liquor.

14. The binder defined in claim 13, in which phenol is incorporated in the reaction product.

15. The binder defined in claim 13 includin sodium silicate.

16. A thermal-setting resin binder in the form of a viscous paste containing the reaction product of furfural and alkalized, concentrated sulfite liquor with which reaction product phenol is incorporated.

17. The binder defined in claim 16, containing ammonium chloride.

18. The binder defined in claim 17, containing resorcinol.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,099,717 Alles Nov. 23, 1937 2,168,160 Hochwalt et al. Aug. 1, 1939 2,184,622 Mauthe et al. Dec. 26, 1939 2,209,289 Wallace July 23, 1940 2,457,357 Fenn Dec. 28, 1948 O'HIER REFERENCES The Technology of Adhesives," Delmonte, 1947, New York, page 313. 

